The present invention relates to mechanical power supplies. It finds particular application in conjunction with creating a high pressure fluid for extensible piston actuators and will be described with particular reference thereto. However, it is to be appreciated that the invention will also find application in conjunction with other high pressure fluid systems, as well as, other mechanical power supplies, such as solenoid type actuators, pumps, motors, valve controllers, and the like.
Heretofore, various sources of mechanical power have been provided. Solenoids are a common extensible actuator. Although solenoids are relatively simple to control and relatively inexpensive, they have several drawbacks. First, solenoids produce relatively little force for their physical size. Second, solenoids generate relatively small starting forces, i.e. they do not generate full force from a dead start. Even once extended, solenoids require full power to remain in their actuated state. Further, under low voltages or marginally higher loads, solenoids stall or fail to pull. Third, the inductive coil can generate RF interference that interferes with electronic control circuitry. Also, solenoids tend to be noisy. They "clack" when pressed open and tend to chatter or buzz under heavy loads.
Electric gear motors are less easy to control than solenoids but produce more force for their physical size. However, gear motors, particularly AC operated gear motors, tend to induce RF interference which interferes with control circuitry. Like a solenoid, gear motors do not start at full force. Gear motors can stall under high start up load conditions. Gear motors tend to be relatively slow. Like solenoids, when first actuated, gear motors draw a large initial surge current. Gear motors tend to be noisy, making a growling sound as they operate.
For higher power densities, hydraulic actuators are commonly utilized. However, the control lines, pumps, fluid reservoirs, pressure regulators, and other associated support devices render hydraulic and pneumatic cylinder assemblies complex to use and space inefficient. Moreover, hydraulic systems tend to be dangerous in a failure mode. When the high pressure fluids are unexpectedly released, the pressure is sufficiently great that they can penetrate or break surrounding structures, injure human attendants either directly and though high pressure oil induced blood poisoning, or the like. Moreover, hydraulic systems tend to be associated with an undesirable whine.
The present invention contemplates a new and improved actuator which overcomes the above-referenced problems and others.